Vibration When Afm Puts Truck In 4 Cylinder Mode

noupf · January 26, 2011

my 2010 ext LTZ 4x4 does this too. The transition from 8 cyl to 4 and back is not "seamless". I also get the vibration when rolling along at low speed ( 30-45 mph ) in v4 mode. I have 3.08's ( the 3.08's are a whole other story grrrrr ) and the 6 speed.........

bigred522 · January 26, 2011

NTrimm, I'm having the same problem with my 2009 LTZ silverado. the only difference is mine has the same vibration in auto 4wd and full 4wd as well as when it's in V-4 mode. It feels similar to a drive shaft vibration, but it's not consistant enough to be a drive shaft issue. I suspect what is happening in one or more of the cylinders that aren't suppose to be firing is that the AFM lifters aren't functioning properly. In otherwords, the fuel is shut off but the valves aren't functioning right. Which would explain why the computer isn't throwing any codes. My service tech has acknowledged that there is a vibration issue, but is at a loss as to what the cause is. It scares me to think their sole source of trouble shooting a problem is computer diagnostics. If it is, they'll never figure this out! By the way, My vibration problem didn't start till I had 30,000 miles on it.

Scott

noupf · January 31, 2011

NTrimm, I'm having the same problem with my 2009 LTZ silverado. the only difference is mine has the same vibration in auto 4wd and full 4wd as well as when it's in V-4 mode. It feels similar to a drive shaft vibration, but it's not consistant enough to be a drive shaft issue. I suspect what is happening in one or more of the cylinders that aren't suppose to be firing is that the AFM lifters aren't functioning properly. In otherwords, the fuel is shut off but the valves aren't functioning right. Which would explain why the computer isn't throwing any codes. My service tech has acknowledged that there is a vibration issue, but is at a loss as to what the cause is. It scares me to think their sole source of trouble shooting a problem is computer diagnostics. If it is, they'll never figure this out! By the way, My vibration problem didn't start till I had 30,000 miles on it.

Scott

What rear end do you have? I have the 3.08 and its happening to me around 40 -50 mph.

I also notice the vibration when I begin to accelerate from a long coasting speed in the neighbor hood of 15-30 mph. An example would be when driving at or around 30mph, then let of to a coast for a little bit, say for a red light ( at this point AFM will now kick in as I am coasting and slowly slowing down to 15-20 mph or so ).......I would then hit the gas pedal to begin acceleration, the engines shutters and vibrates a little as the AFM is going from 4 cyl to 8 cycl. Its hardly a seamless transition and becoming very annoying.

I pretty much just keep my truck in M5 when around town ( under 50 mph ).......but I shouldnt have to do this.

ntrimm · February 1, 2011

NTrimm, I'm having the same problem with my 2009 LTZ silverado. the only difference is mine has the same vibration in auto 4wd and full 4wd as well as when it's in V-4 mode. It feels similar to a drive shaft vibration, but it's not consistant enough to be a drive shaft issue. I suspect what is happening in one or more of the cylinders that aren't suppose to be firing is that the AFM lifters aren't functioning properly. In otherwords, the fuel is shut off but the valves aren't functioning right. Which would explain why the computer isn't throwing any codes. My service tech has acknowledged that there is a vibration issue, but is at a loss as to what the cause is. It scares me to think their sole source of trouble shooting a problem is computer diagnostics. If it is, they'll never figure this out! By the way, My vibration problem didn't start till I had 30,000 miles on it.

Scott

This AFM vibration is becoming a huge issue for GM now and will only get bigger if they do not find a solution to the problem. Your issue in particular sounds like the lifters have went bad in the 30,000 miles since the problem did not present until the 30,000 miles. There is or was a TSB on the lifters a while back. I do know of some people that bought handheld programmers and turned the AFM/DOD off and there problem went away. This tells me that there is more than likely a programming issue from GM. There are a lot of variables....Speed, RPM, Gear the tranny is in, Load on the car, etc. all of which should be programmable. There has to be a programmable fix to their problem but Im not sure their car will meet emissions standards if they change the software???

ChevyTech77 · February 1, 2011

When you shut 4 cylinders of an 8 cylinder engine off, that was balanced to run on 8 cylinders, you're going to have some vibration. While GM engineering has spent countless hours on displacing that vibration, I can't see ALL of it going completely away. Time will tell though.

ntrimm · February 1, 2011

When you shut 4 cylinders of an 8 cylinder engine off, that was balanced to run on 8 cylinders, you're going to have some vibration. While GM engineering has spent countless hours on displacing that vibration, I can't see ALL of it going completely away. Time will tell though.

ChevyTech77,

Thanks for chiming in on this. Im hoping, for all consumers sake, that GM finds a solution to the this issue. I personally think the only solution is for GM to do away with AFM.

bigred522 · February 4, 2011

ChevyTech77,

Thanks for the input! After some intense research and discussion with a couple gm techs, I've come to the conclusion that some of the vibration I'm feeling may be coming from the exhaust system vibrating. Apparently there is a TB out there that suggests adding some weight to key parts on the exhaust to reduce the vibration. If this works then I'm golden! I just don't want my engine crappin out 10,000 miles after the warranty runs out, only to find it was something that could/should have been fixed when it was under warranty! LOL As for the 4wd vibration, that is looking more and more like a bad u-joint in the front drive shaft. I'm scheduled to bring it in this wednesday so they can put a vibration sensor on it. we'll see what happens!

trmck · March 28, 2011

Any update on this topic? I have a 2010 Silverado LT 5.3 with a 3.42 rear... same problem. I have access to GM's globalconnect and have been checking for an updated TSB with a fix but have had no luck. As a former GM service writer I know I've exhausted my options at a dealership level

mattymax · April 11, 2011

Any updates ??

2007' 5.3AFM 26,000 miles

I get it some times when the truck stays in 4cyl for a good amount time, say at like 50 or 60, and I start to slow down, then transition back to 8cyl...the transition back to 8cyl is a little vibration. I get none from 8cyl to 4cyl...

Hear me out:

It kinda feels like the road....

I have a feeling that when its in 4cyl its "Coasting" more then when its 8cyl...maybe its the imperfection in the road causing this....

The reason I think this is because I DEFINETLY DONT get it EVERYTIME...Its only certain times on way home, only certain road conditions

-matt

Edited April 11, 2011 by mattymax

abschnick · May 26, 2011

I have the exact same issue with my 07 Sierra cc nnbs. When it drops into v4 mode, usually at highway speed, I start to get a slight vibration. Almost like a humming noise. As soon as I hit the gas and it goes into v8 the vibration goes away. Seems like it only does it when traveling at a constant speed in the v4 mode. Very annoying.

ERIE_ONE · May 30, 2011

2011 Silverado 1/2 ton ext cab Z71 3:42 gears

I noticed mine within the 2nd - 3rd week of ownership. My original thought was that my conservative driving "taught" the computer to shift WAY too early and allow V4 mode to engage WAY to early. The trans has seemed to get more confused over time as well, short shifting ALOT more lately. I only have about 4k on the truck now. I bought the truck in January during some very icey / snowy conditions so the truck "learned" under very conservative driving conditions. I have considered disconnecting the battery to have it "re-learn" during summer months when I'm not driving extra conservative, however I dont know if the truck is constantly "learning" or exactly how this works. Why does my truck need to learn anyways? I bought it for who it was in the beginning..

Why cant I have a button to just turn it off? Econo mode button, let me decide when I need to conserve fuel. My wifes new Equinox has a econo mode, put one in the trucks too. JMO

Please keep this thread updated! Very interested in the resolve to this issue.

Edited May 30, 2011 by ERIE_ONE

spikesputnik · June 3, 2011

My '09 Silvy 5.3 3.42 was seamless when stock. At about 10K miles I got it tuned and AFM turned off and it ran great. Put a Magnaflow on and it was fine as far as no vibrations ( but did have some preignition rattling issues at about 1500rpm, sometimess fuel quality related?). So I sent the tuned ECM back for some retuning and put the stock ECM back on -> immediately got vibrations when in V-4 mode- sounds like a diesel semi when decelerating when I'm at steady speed. It stays in V-4 much more than I would expect, even when pulling a 4K# boat at 50 mph and in trailering tranny mode. Can't wait to get my tuned and AFM turned off ECM back!!! Just hoping that no lifter damage is happening as I'm driving it now...

Edited June 3, 2011 by downsized

agrats84 · August 9, 2011

Any updates on this? I have an 09' 5.3 LTZ with 31,000 miles and am getting this vibration more than ever. Has anyone with a BB tune taken it back to the dealer? I know Justin can turn off AFM, but I want to make sure no other damage is being done. I want to solve this before my warranty runs out!

bhaluszka · May 7, 2015

Document ID: 4080736

#PI1413: Diagnostic Tip for Vibration, Shudder or Roughness While Driving at Low Steady Speeds in V4 Mode - (Feb 12, 2015)

Subject: Diagnostic Tip for Vibration, Shudder or Roughness While Driving at Low Steady Speeds in V4 Mode

Models: 2011 Cadillac Escalade Models 2011 Chevrolet Avalanche, Camaro, Silverado, Suburban, Tahoe 2011 GMC Sierra, Yukon Models Equipped with Active Fuel Management V8 Engines (RPOs LC9, LMG, LZ1, L77, L94, L99) and 6L80 Automatic Transmission (RPO MYC)

Attention: This PI also applies to any of the above models that may be Export vehicles. Condition/Concern

Some customers may comment on a vibration, shudder or roughness while driving at low speeds with a steady throttle on a level road.

Customers may also comment that the condition is more noticeable when driving up an incline.

This concern will be most noticeable when the vehicle is operating in 4V mode, Active Fuel Management (AFM).

Recommendation/Instructions

The root cause of this concern may be a broken torque converter clutch regulator valve spring (353) in the lower valve body, causing the torque converter clutch (TCC) slip speed to drop to zero.

Monitor the TCC slip speed during the concern while driving with a steady throttle input. If the TCC slip speed is a constant zero RPM during the concern, inspect the lower valve body for a broken torque converter clutch regulator valve spring (353).

Note: During the road test, the TCC slip may momentarily drop to zero and then climb to 30-50 RPM of slip. This is the normal operation of the TCC.

If the torque converter clutch regulator valve spring (353) is broken, replace the lower valve body.

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.

BlackZ71Silverado · May 21, 2015

Welcome to the wonderful world of GM's AFM. This has been a complaint since day one and GM still has no fix and is still advertising AFM as "seamless", it's anything but. Both my AFM trucks did this and the GM tech. clowns said it's normal, they don't know what they are talking about. Solved the issue with tunes, no more AFM!

Sorry to hear you have the dreaded AFM vibration but you are not alone. Other than playing games with the genius tech's at dealerships who say it's normal, then some say not normal, the fix it tuning it out. A tune or that Range device can help you. Other than that it seems like GM wants us to just deal with it and get ysed to it.

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